/**
 * Copyright (C) <2019>  <chen junwen>
 *
 * This program is free software: you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program.  If
 * not, see <http://www.gnu.org/licenses/>.
 */
package io.mycat.util;

import java.io.Closeable;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;

/**
 * @author jamie12221
 *  date 2019-05-07 21:36
 * 堆内数组自动增长类
 * todo 性能优化
 **/

public class ByteArrayOutput implements Closeable {

  /**
   * The buffer where data is stored.
   */
  protected byte[] buf;

  /**
   * The number of valid bytes in the buffer.
   */
  protected int count;

  /**
   * Creates a new byte array output stream. The buffer capacity is initially 32 bytes, though its
   * size increases if necessary.
   */
  public ByteArrayOutput() {
    this(256);
  }

  /**
   * Creates a new byte array output stream, with a buffer capacity of the specified size, in
   * bytes.
   *
   * @param size the initial size.
   * @throws IllegalArgumentException if size is negative.
   */
  public ByteArrayOutput(int size) {
    if (size < 0) {
      throw new IllegalArgumentException("Negative initial size: "
                                             + size);
    }
    buf = new byte[size];
  }

  /**
   * Increases the capacity if necessary to ensure that it can hold at least the number of elements
   * specified by the minimum capacity argument.
   *
   * @param minCapacity the desired minimum capacity
   * @throws OutOfMemoryError if {@code minCapacity < 0}.  This is interpreted as a request for the
   * unsatisfiably large capacity {@code (long) Integer.MAX_VALUE + (minCapacity -
   * Integer.MAX_VALUE)}.
   */
  private void ensureCapacity(int minCapacity) {
    // overflow-conscious code
    if (minCapacity - buf.length > 0) {
      grow(minCapacity);
    }
  }

  /**
   * The maximum size of array to allocate. Some VMs reserve some header words in an array. Attempts
   * to allocate larger arrays may result in OutOfMemoryError: Requested array size exceeds VM
   * limit
   */
  private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

  /**
   * Increases the capacity to ensure that it can hold at least the number of elements specified by
   * the minimum capacity argument.
   *
   * @param minCapacity the desired minimum capacity
   */
  private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = buf.length;
    int newCapacity = oldCapacity << 1;
    if (newCapacity - minCapacity < 0) {
      newCapacity = minCapacity;
    }
    if (newCapacity - MAX_ARRAY_SIZE > 0) {
      newCapacity = hugeCapacity(minCapacity);
    }
    buf = Arrays.copyOf(buf, newCapacity);
  }

  private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) // overflow
    {
      throw new OutOfMemoryError();
    }
    return (minCapacity > MAX_ARRAY_SIZE) ?
               Integer.MAX_VALUE :
                                     MAX_ARRAY_SIZE;
  }

  /**
   * Writes the specified byte to this byte array output stream.
   *
   * @param b the byte to be written.
   */
  public void write(int b) {
    ensureCapacity(count + 1);
    buf[count] = (byte) b;
    count += 1;
  }

  /**
   * Writes <code>len</code> bytes from the specified byte array starting at offset <code>off</code>
   * to this byte array output stream.
   *
   * @param b the data.
   * @param off the start offset in the data.
   * @param len the number of bytes to write.
   */
  public void write(byte[] b, int off, int len) {
    if ((off < 0) || (off > b.length) || (len < 0) ||
            ((off + len) - b.length > 0)) {
      throw new IndexOutOfBoundsException();
    }
    ensureCapacity(count + len);
    System.arraycopy(b, off, buf, count, len);
    count += len;
  }

  /**
   * Writes the complete contents of this byte array output stream to the specified output stream
   * argument, as if by calling the output stream's write method using <code>out.write(buf, 0,
   * count)</code>.
   *
   * @param out the output stream to which to write the data.
   * @throws IOException if an I/O error occurs.
   */
  public void writeTo(OutputStream out) throws IOException {
    out.write(buf, 0, count);
  }

  public void write(byte[] b) {
    write(b, 0, b.length);
  }

  /**
   * Resets the <code>count</code> field of this byte array output stream to zero, so that all
   * currently accumulated output in the output stream is discarded. The output stream can be used
   * again, reusing the already allocated buffer space.
   *
   *
   */
  public void reset() {
    count = 0;
  }

  /**
   * Creates a newly allocated byte array. Its size is the current size of this output stream and
   * the valid contents of the buffer have been copied into it.
   *
   * @return the current contents of this output stream, as a byte array.
   * @see java.io.ByteArrayOutputStream#size()
   */
  public byte[] toByteArray() {
    return Arrays.copyOf(buf, count);
  }

  /**
   * Returns the current size of the buffer.
   *
   * @return the value of the <code>count</code> field, which is the number of valid bytes in this
   * output stream.
   *
   */
  public int size() {
    return count;
  }

  /**
   * Converts the buffer's contents into a string decoding bytes using the platform's default
   * character set. The length of the new <tt>String</tt> is a function of the character set, and
   * hence may not be equal to the size of the buffer.
   *
   * <p> This method always replaces malformed-input and unmappable-character
   * sequences with the default replacement string for the platform's default character set. The
   * {@linkplain java.nio.charset.CharsetDecoder} class should be used when more control over the
   * decoding process is required.
   *
   * @return String decoded from the buffer's contents.
   * @since JDK1.1
   */
  public String toString() {
    return new String(buf, 0, count);
  }

  /**
   * Converts the buffer's contents into a string by decoding the bytes using the named {@link
   * java.nio.charset.Charset charset}. The length of the new
   * <tt>String</tt> is a function of the charset, and hence may not be equal
   * to the length of the byte array.
   *
   * <p> This method always replaces malformed-input and unmappable-character
   * sequences with this charset's default replacement string. The {@link
   * java.nio.charset.CharsetDecoder} class should be used when more control over the decoding
   * process is required.
   *
   * @param charsetName the name of a supported {@link java.nio.charset.Charset charset}
   * @return String decoded from the buffer's contents.
   * @throws UnsupportedEncodingException If the named charset is not supported
   * @since JDK1.1
   */
  public String toString(String charsetName)
      throws UnsupportedEncodingException {
    return new String(buf, 0, count, charsetName);
  }

  /**
   * Creates a newly allocated string. Its size is the current size of the output stream and the
   * valid contents of the buffer have been copied into it. Each character <i>c</i> in the resulting
   * string is constructed from the corresponding element <i>b</i> in the byte array such that:
   * <blockquote><pre>
   *     c == (char)(((hibyte &amp; 0xff) &lt;&lt; 8) | (b &amp; 0xff))
   * </pre></blockquote>
   *
   * @param hibyte the high byte of each resulting Unicode character.
   * @return the current contents of the output stream, as a string.
   * @see java.io.ByteArrayOutputStream#size()
   * @see java.io.ByteArrayOutputStream#toString(String)
   * @see java.io.ByteArrayOutputStream#toString()
   * @deprecated This method does not properly convert bytes into characters. As of JDK&nbsp;1.1,
   * the preferred way to do this is via the
   * <code>toString(String enc)</code> method, which takes an encoding-name
   * argument, or the <code>toString()</code> method, which uses the platform's default character
   * encoding.
   */
  @Deprecated
  public String toString(int hibyte) {
    return new String(buf, hibyte, 0, count);
  }

  @Override
  public void close() {

  }
}